A new method for the synthesis of poly(dichlorophosphazene) at ambient temperatures is described. It involves the initiation of Cl3PNSiMe3 with small amounts of PCl5 in CH2Cl2 to yield poly(dichlorophosphazene), (NPCl2) n , with narrow polydispersities. The molecular weight of poly(dichlorophosphazene) was controlled by altering the ratio of monomer to initiator. The polymer chains were found to be active after chain propagation since further addition of monomer resulted in the formation of higher molecular weight polymer. Integration of 1H and 31P NMR spectra of these reactions revealed that the polymerization follows first-order reaction kinetics with respect to monomer concentration. Active polymer chains may be quenched or end-capped by the addition of trace quantities of Me2(CF3CH2O)PNSiMe3 or (CF3CH2O)3PNSiMe3. Furthermore, PBr5, SbCl5, and Ph3C[PF6] were also found to be effective initiators in CH2Cl2 at room temperature.

In infants with acute moderate-to-severe bronchiolitis who were treated in the emergency department, a single dose of 1 mg of oral dexamethasone per kilogram did not significantly alter the rate of hospital admission, the respiratory status after 4 hours of observation, or later outcomes. (ClinicalTrials.gov number, NCT00119002 [ClinicalTrials.gov].).

A new, ambient-temperature method for the direct synthesis of organo-substituted polyphosphazenes is described. It involves the initiation of a series of organophosphoranimines R(R′)-with catalytic amounts of PCl5 in CH2Cl2 to yield (after treatment with NaOCH2CF3 in the case of 3) the corresponding polyphosphazene species (NdPRR′)n (4, R ) Ph, R′ ) OCH2CF3; 6, R) with narrow polydispersities. The molecular weights of the polyphosphazenes were controlled by altering the ratio of monomer to initiator. The polymer chains were found to be active after chain propagation since further addition of monomer resulted in the formation of higher molecular weight polymer. For monomers 7 and 9 optimum polymerization behavior was found to occur at 35 °C in the absence of solvent in the presence of catalytic quantities of PCl5. These reactions proceeded to 100% completion, while maintaining molecular weight control and narrow polydispersites. In the case of polymers 4, 8, and 10, which were synthesized with a 10:1 monomer to initiator ratio in CH2Cl2, the resultant polymers were analyzed by gel permeation chromatography (GPC) (4, Mn ) 2.9 × 10 3 , polydispersity (PDI ) Mw/Mn) ) 1.07); 8, Mn ) 2.2 × 10 3 , PDI ) 1.31; 10, Mn ) 7.8 × 10 3 , PDI ) 1.23). Poly(diphenylphosphazene), ( NdPPh2)n ( 6), was insoluble in common organic solvents and was characterized by magic angle spinning (MAS) solid state 31 P NMR spectroscopy. The effects of side group steric bulk, electron-withdrawing or -donating properties, and leaving group types on the ambient-temperature cationic induced polymerizations are discussed.

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